Photolithography has been widely employed to form fine electric circuits such as ICs and LSIs; for example, a photoresist layer is formed of a photoresist containing an alkali-soluble resin or another material on a conductive layer which has been formed on a circuit substrate, the product is irradiated with light through a photomask having the pattern of a conductive circuit, an electric circuit is formed, for instance, by removing part of the conductive layer corresponding to part of the resist layer other than part of the resist layer patterned with the electric circuit (removing part of the resist layer not irradiated with light and removing part of the conductive layer corresponding thereto), and the unnecessary part of the photoresist layer is optionally removed. This technique, however, includes several processes, such as irradiation with light through a photomask, and is thus complicated. Hence, such a technique has disadvantages such as the increased number of processes and high production costs.
Transistors used in ICs and LSIs have been widely employed as essential electronic devices used for producing television sets and computer equipment and, nowadays, have been produced with use of an inorganic material, such as silicon, as the main material. In recent years, attentions have been paid to organic transistors in which organic substances are used as the material of the transistors.
In such a circumstance, the field of printable electronics in which organic substance-containing inks can be used to reduce the number of processes and production costs has been attracting attention, and printing of electrical wiring by a variety of printing techniques, such as inkjet printing, screen printing, and gravure offset printing, has been studied. Among these printing techniques, inkjet printing is a printing technique which does not need use of a printing plate, therefore eliminates a process and cost for producing a printing plate, and is useful for on-demand printing; hence, the inkjet printing has been a promising technique for producing a variety of products in a small quantity.
In recent years, in view of using electronic equipment in ubiquitous environments, techniques which enable high-density packaging (formation of fine circuits) at low cost has been demanded to form circuit wiring in such electronic equipment. In a known technique among these techniques, for example, printing is carried out by an inkjet recording technique with a water-based ink containing nanometer-order metal particles as a component thereof, and then firing is carried out at not more than 180° C. to form conductive wiring (see Patent Literature 1).
In order to prepare the water-based conductive ink for inkjet recording, which has been disclosed in Patent Literature 1, glycerin is used as a polyhydric alcohol; however, conductive wiring formed with use of such an ink has an insufficient conductivity.